The present invention relates to a battery removal indicator for battery operated units such as smoke detectors.
In many safety devices, a battery for supplying power is mounted within a cover. As a result, it is difficult to ascertain whether the battery is present or absent. Records have shown that two-thirds of smoke detectors which have been found not to respond in real life fire situations were without batteries.
Earlier, larger smoke detectors such as the GE Home Sentry Smoke Alarm Model 8201-101 were made with rotating warning flags which would deploy from under the cover if no battery was present. The flags were spring loaded and retained by a latch arrangement controlled by a lever retained under a 12 volt battery. This arrangement required a large amount of space, was expensive to produce, and was dependent upon uniform sized batteries. This system did not survive when the smoke detector industry changed over to smaller units powered by 9 volt batteries with high dimensional variability.
In other smoke detectors, gravity operated indicators were used to provide a visual indication that a battery was not present. U.S. Pat. No. 4,228,428 to Niedermeyer illustrates such a visual indicator. In the Niedermeyer patent, the visual indicator is formed by a cover of the smoke detector. The cover is hinged at one end and has a retaining clip secured to an inner surface at an opposite end. The clip has two arms each of which engage a respective side of a battery. When the battery is present in the detector, the cover is held in place by the engagement between the clip and the battery. When the battery is absent, the cover hangs down because there is nothing for the clip to engage. Problems arise with this type of visual indicator when the smoke detector is mounted incorrectly to a vertical surface. For example, if the smoke detector is inadvertently mounted to the vertical surface with the hinged end of the cover at the top, gravity will cause the cover to sit in a substantially closed position even though the battery is absent.
Accordingly, it is an object of the present invention to provide an improved battery removal indicator which functions irrespective of the orientation of the battery operated device.
It is a further object of the present invention to provide an improved battery removal indicator which is unaffected by battery dimensions.
It is yet a further object of the present invention to provide an improved battery removal indicator as above which provides two distinct visual signals.
It is still another object of the present invention to provide an improved battery removal indicator as above which is relatively inexpensive to produce.
These and other objects and advantages will become more apparent from the following description and drawings in which like reference numerals depict like elements.